Preparation method of biochar improved by acidic deep-eutectic solvent and application of biochar in degradation of fomesafen

Abstract

The invention discloses a preparation method of biochar improved by an acidic deep-eutectic solvent and application of the biochar in degradation of fomesafen, and relates to the technical field of water pollution treatment and environmental functional materials. The preparation method comprises the following steps: mixing biomass powder and an acidic deep-eutectic solvent, and carrying out heating reflux reaction to obtain biochar; the acidic eutectic solvent takes choline chloride as a hydrogen bond acceptor and methanesulfonic acid as a hydrogen bond donor. By introducing the acidic eutectic solvent, the conditions of the traditional hydrothermal carbonization method are optimized, and hydrothermal carbonization of biomass can be carried out at normal pressure and 200 DEG C or below. In addition, efficient degradation of fomesafen pesticide residues in a water body is realized by utilizing the biochar activated persulfate optimally prepared by the method, and the biochar activated persulfate shows good degradation performance in a neutral to alkalescent water environment and can be used for purification treatment of pesticide polluted water bodies.

Description

Technical Field

[0001] This invention relates to the fields of water pollution control and environmental functional materials technology, and in particular to a method for preparing biochar modified with an acidic eutectic solvent and its application in the degradation of flusulfanilamide. Background Technology

[0002] Flumetsulam is a persistent herbicide with a long residual period. Furthermore, flumetsulam is a weakly acidic herbicide with good water solubility and a soil adsorption coefficient (Koc) of approximately 60-100 mL / g, indicating a moderately weak soil adsorption capacity. It is particularly prone to migration with water in sandy soils with low organic matter content, posing a certain risk of leaching of residual flumetsulam in the soil. Although flumetsulam is a low-toxicity herbicide, its high usage and long residual characteristics pose potential threats to the ecological environment and human health. Therefore, it is essential to remove flumetsulam pesticide residues from environmental media through green and efficient methods.

[0003] Currently, the most efficient pesticide pollution remediation measures mainly include physical, chemical, and biological methods. Chemical remediation typically refers to methods such as chemical oxidation and catalytic degradation. These methods offer high degradation efficiency and allow for in-situ remediation. They include passivation, photocatalytic degradation, and advanced oxidation processes (AOPs). Due to their high efficiency and low cost, they are widely used to remove pesticides, antibiotics, polycyclic aromatic hydrocarbons, and other organic pollutants from the environment. Advanced oxidation processes (AOPs) are highly efficient chemical remediation technologies that use light, heat, electricity, and metal ions to stimulate oxidants and generate highly reactive free radicals, transforming pollutants into low-toxicity and non-toxic degradation products. As a chemical technology capable of degrading and removing persistent and recalcitrant pollutants, AOPs have shown great potential in removing pesticide pollutants from the environment. Among them, sulfate-based advanced oxidation processes (SR-AOPs) have advantages such as high oxidation potential, wide applicable pH range, and long free radical half-life, and have been widely used in pesticide pollution remediation. Persulfates used as oxidants for AOPs include permonosulfate (PMS) and perdisulfate (PDS). Chemically, PDS has a symmetrical structure, lower bond energy, and is more water-soluble, making it easier to store and more widely used. Persulfates contain high-energy peroxy bonds. Persulfate-based AOPs require energy application or the introduction of activators to generate reactive free radicals from these peroxy bonds for oxidative degradation. Activation systems for AOPs include homogeneous and heterogeneous systems. Heterogeneous activation systems primarily utilize heterogeneous activators to activate the oxidative degradation system. Compared to homogeneous systems, heterogeneous systems consume less energy, are easier to recycle, and are less likely to cause secondary pollution, making them more suitable for processing large quantities of contaminated samples.

[0004] Biochar (BC) is a novel, environmentally friendly, and low-cost green carbon material. It is typically a solid carbon material produced by thermochemical conversion of organic biomass such as agricultural, forestry, and municipal waste. It possesses advantages such as a large specific surface area and abundant functional groups, showing great potential for applications in pollutant adsorption, photoelectrocatalysis, and advanced oxidation activation. As a high-performance carbon-based material, biochar is currently widely used as a heterogeneous activator for organic pollutants (AOPs). Compared to other carbon-based materials such as graphene and carbon nanotubes, biochar exhibits advantages such as ease of preparation, low cost, wide availability, and environmental friendliness. Furthermore, the specific surface area, surface functional groups, porosity, and other physicochemical properties of biochar can be functionalized and controlled through various methods, and functional units can be loaded onto it. These characteristics make biochar-activated persulfate removal of pesticide residues in environmental media a promising prospect. The mechanism of biochar-activated persulfate oxidation degradation of environmental organic pollutants mainly includes two pathways: free radical pathway and non-free radical pathway. Oxygen-containing functional groups, defect structures, and electron transfer on the biochar surface are its main active sites and modes of action.

[0005] The main methods for preparing biochar include pyrolysis and hydrothermal carbonization. While pyrolysis (especially at high temperatures, such as above 500 °C) can produce biochar with high carbon content and stable structure, this process typically consumes large amounts of energy (such as electricity and natural gas), easily generates greenhouse gases, and has high equipment investment and operating costs, which limits its large-scale application to some extent. Furthermore, high-temperature pyrolysis may result in relatively low biochar yields, and the surface oxygen-containing functional groups may sometimes be insufficient, potentially affecting its activation performance. In contrast, hydrothermal carbonization, a method of converting biomass into biochar in a closed container using water as a solvent, offers relatively mild reaction conditions (typically 250-374 °C), utilizes water as a green solvent, and the prepared biochar is usually rich in oxygen-containing functional groups on its surface, giving it unique advantages for certain applications. However, traditional hydrothermal carbonization methods typically require high temperature and pressure (250-374 ℃ and 4-22 MPa), demanding sophisticated equipment, long reaction times (usually tens of hours), low efficiency, and often cumbersome post-processing steps such as washing and drying. Furthermore, biochar prepared using existing conventional methods may not effectively activate persulfate, failing to achieve efficient degradation and removal of recalcitrant pollutants such as flusulfanilamide. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing biochar using an acidic eutectic solvent and its application in the degradation of flusulfanilamide, thereby addressing the problems existing in the prior art. This invention provides a method for preparing biochar using an acidic eutectic solvent, which can efficiently prepare biochar. Based on this, advanced oxidation technology is combined with improved corn stalk biochar as an activator, and a biochar-persulfate catalytic oxidation system is constructed using a persulfate oxidant and applied to the degradation and removal of flusulfanilamide residues in the environment.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] One of the technical solutions of the present invention: a method for preparing biochar using an acidic eutectic solvent, comprising the following steps:

[0009] Biochar is obtained by mixing biomass powder with an acidic eutectic solvent and heating under reflux (i.e., carbonization reaction).

[0010] The acidic eutectic solvent uses choline chloride as a hydrogen bond acceptor and methanesulfonic acid as a hydrogen bond donor.

[0011] Eutectic solvents are eutectic mixtures composed of hydrogen bond donors and acceptors, possessing excellent properties such as low toxicity, low vapor pressure, ease of preparation, and low cost. This invention uses an eutectic solvent as a substitute for water in the hydrothermal carbonization process. The acidic eutectic solvent system can disrupt the ether bonds in lignocellulosic biomass, thereby achieving the purpose of deconstructing the biomass structure and promoting its conversion into biochar. In other words, this invention optimizes and improves the hydrothermal carbonization preparation method of biochar by introducing an acidic eutectic solvent, thus optimizing the conditions for biochar preparation using the hydrothermal carbonization method.

[0012] In addition, the acidic eutectic solvent prepared by the present invention using methanesulfonic acid as a hydrogen bond donor can dope sulfur on the surface of biochar, thereby changing the electron distribution on the surface of biochar and enhancing the electron transfer ability of the biochar surface. Furthermore, the CSC covalent bonds and thiophene-type structures formed by sulfur doping in biochar can serve as effective active sites for activating persulfate and generating active species such as sulfate radicals, thereby improving the ability of biochar to activate persulfate.

[0013] Furthermore, the preparation steps of the acidic eutectic solvent include: mixing choline chloride and methanesulfonic acid, heating and stirring to obtain the eutectic solvent.

[0014] Furthermore, the molar ratio of choline chloride to methanesulfonic acid is 1:1-1.5, preferably 1:1.

[0015] Furthermore, the heating and stirring temperature is 80-100 ℃, and the time is 1-3 h.

[0016] Furthermore, the mass ratio of the biomass powder to the acidic eutectic solvent is 1.5:20-30, preferably 1.5:25.

[0017] Furthermore, the temperature of the heating reflux reaction is 90-150 ℃, preferably 150 ℃; the time is 2-5 h, preferably 5 h.

[0018] Furthermore, the biomass powder is obtained by drying and pulverizing corn stalks.

[0019] Furthermore, the heating and reflux reaction is carried out under stirring conditions, with the stirring speed being 200-400 rpm.

[0020] The second technical solution of the present invention: a biochar prepared by a biochar preparation method improved by the above-mentioned acidic eutectic solvent.

[0021] The third technical solution of the present invention: the application of the above-mentioned biochar in the activation of persulfate degradation of flumethrin in water.

[0022] Furthermore, the application steps include: adding persulfate and the above-mentioned biochar to the water containing flusulfanilamide to carry out a degradation reaction.

[0023] Persulfate is activated on the surface of biochar to generate a series of strong oxidizing free radicals, including sulfate free radicals and hydroxyl free radicals, thereby degrading flusulfanilamide molecules.

[0024] Furthermore, the persulfate includes sodium persulfate (Na2S2O8, abbreviated as PDS).

[0025] Furthermore, the degradation reaction is carried out at 20-30°C and pH=7-9.

[0026] Preferably, the concentration of flusulfanilamide in the water is 30-50 mg / L, the amount of sodium persulfate added is 4-6 mM, and the amount of biochar added is 0.2-0.4 g / L.

[0027] This invention optimizes the hydrothermal carbonization process for biochar by introducing an acidic eutectic solvent, providing a new approach for the efficient and green conversion and utilization of agricultural waste straw while optimizing the conditions for biochar preparation via hydrothermal carbonization. Based on this, and combining advanced oxidation technology, the improved corn straw biochar is used as an activator, and a biochar-persulfate catalytic oxidation system is constructed using persulfate oxidant. This system is then applied to the degradation and removal of flumethrin residues in the environment.

[0028] The present invention discloses the following technical effects:

[0029] (1) This invention uses an acidic eutectic solvent as a hydrothermal carbonization solvent to replace water and develops an efficient method for preparing biochar hydrothermal carbonization. Biochar materials (ChCl-MS-BC) can be rapidly prepared under normal pressure and low temperature conditions.

[0030] (2) This invention uses corn stalk waste biomass as raw material, which has the advantages of readily available raw materials and low cost, realizing waste recycling and utilization, and has environmental protection significance.

[0031] (3) This invention constructs a ChCl-MS-BC / PDS catalytic system to efficiently degrade flumethrin pesticide residues in water, achieving a removal rate of >90% for flumethrin in water within 100 min. The ChCl-MS-BC biochar material of this invention exhibits excellent activation catalytic efficiency in the degradation of pesticide pollutants.

[0032] (4) The ChCl-MS-BC biochar material of the present invention exhibits excellent adaptability under different water chemistry conditions. When common anions (such as Cl-) are present in the water... - NO3 - When sodium persulfate is used, its degradation efficiency for flusulfanil is only slightly affected, and it still maintains a high removal rate. It can effectively activate sodium persulfate to degrade flusulfanil within a wide initial pH range (approximately 7-9).

[0033] (5) The ChCl-MS-BC biochar material of the present invention can be recycled after the degradation reaction is completed.

[0034] In summary, the biochar preparation method and its application method provided by this invention have both ease of preparation and excellent functionality, and can efficiently and sustainably remove flusulfanilamide from water, showing good prospects for practical application. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 The images show SEM images of ChCl-MS-BC biochar prepared by carbonization at different temperatures in Examples 1-4. In the images, a) and b) show the morphology of ChCl-MS-BC prepared by carbonization at 90 ℃ and 110 ℃, respectively, and c) and d) show the morphology of ChCl-MS-BC prepared by carbonization at 130 ℃ and 150 ℃, respectively.

[0037] Figure 2 EDS image of the ChCl-MS-BC biochar prepared in Example 1.

[0038] Figure 3 The infrared spectra of ChCl-MS-BC biochar prepared by carbonization at different temperatures in Examples 1-4 are shown.

[0039] Figure 4 XPS scan characterization images of ChCl-MS-BC biochar prepared by carbonization at different temperatures in Examples 1-4 are shown, where a is the fitting result of C1s and b is the fitting result of O1s.

[0040] Figure 5 Performance test results of biochar prepared by carbonization with different acidic eutectic solvents (biochar prepared in Example 1 and Comparative Examples 1-6) activating PDS to degrade flusulfanilamide.

[0041] Figure 6 The results show the effect of different pH values ​​on the degradation performance of flumethrin by ChCl-MS-BC activated PDS.

[0042] Figure 7 The effect of different free radical quenchers on the degradation of flusulfanilamide in the ChCl-MS-BC / PDS system is shown in Figure (a) and the spectrum of active free radicals detected by electron paramagnetic resonance (EPR) is shown in Figure (bd). Detailed Implementation

[0043] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0044] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0045] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0046] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0047] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0048] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0049] In the following embodiments and comparative examples of the present invention, room temperature refers specifically to 20-30°C.

[0050] Unless otherwise specified, all raw materials used in the following embodiments and comparative examples of this invention are commercially available products.

[0051] Example 1

[0052] A method for preparing biochar using an acidic eutectic solvent, comprising the following steps:

[0053] (1) Preparation of acidic eutectic solvent: Choline chloride (ChCl) and methanesulfonic acid (MS) were added to a 100 mL round-bottom flask in a 1:1 molar ratio. After the flask was sealed with a glass stopper, it was placed in a constant temperature oil bath for heating and stirring. The product was collected after heating and stirring at 80 °C for 2 h until a colorless and transparent liquid was obtained. This product is the acidic eutectic solvent.

[0054] (2) Preparation of corn stalk biochar: Corn stalk waste was selected as biomass raw material. The corn stalks were dried, crushed, and passed through a 200-mesh sieve to obtain corn stalk biochar powder. First, 1.50 g of corn stalk biochar powder was weighed and added to a 100 mL round-bottom flask. Then, 25 g of the prepared acidic eutectic solvent was added to the flask as the carbonization solvent. A condenser was installed above the flask for reflux, and the heating and reflux reaction (i.e., carbonization reaction) was carried out at 150 °C for 5 h. During the reaction, the mixture was stirred at a constant speed of 300 rpm. After the reaction was complete, the mixture in the flask was poured into a 50 mL centrifuge tube and centrifuged at 3800 rpm for 5 min to separate the solid and liquid mixture into layers. After filtering to remove the supernatant, 50 mL of distilled water was added and the solid product was washed by shaking and then filtered. The product was then washed three times alternately with distilled water and anhydrous ethanol. Finally, it was transferred to a glass petri dish and placed in a vacuum drying oven at 60 °C for 12 h to obtain biochar material, denoted as ChCl-MS-BC, or simply 150 °C-BC, which was stored in a desiccator for later use.

[0055] Example 2

[0056] Same as Example 1, except that the heating reflux reaction (i.e. carbonization reaction) was adjusted to 90 °C, and the resulting biochar material is referred to as 90 °C-BC.

[0057] Example 3

[0058] Same as Example 1, except that the heating reflux reaction (i.e. carbonization reaction) was adjusted to 110 °C, and the resulting biochar material is referred to as 110 °C-BC.

[0059] Example 4

[0060] Same as Example 1, except that the heating reflux reaction (i.e. carbonization reaction) was adjusted to 130 °C, and the resulting biochar material is simply referred to as 130 °C-BC.

[0061] Comparative Example 1

[0062] Same as Example 1, except that the acidic eutectic solvent was prepared from choline chloride (ChCl) and formic acid (FA) in a molar ratio of 1:1. The preparation conditions of the acidic eutectic solvent and the preparation conditions of corn straw biochar were the same as in Example 1. The final biochar material was denoted as ChCl-FA-BC.

[0063] Comparative Example 2

[0064] Same as Example 1, except that the acidic eutectic solvent was prepared from choline chloride (ChCl) and acetic acid (AcA) in a molar ratio of 1:1. The preparation conditions of the acidic eutectic solvent and the preparation conditions of corn straw biochar were the same as in Example 1. The final biochar material was denoted as ChCl-AcA-BC.

[0065] Comparative Example 3

[0066] Same as Example 1, except that the acidic eutectic solvent was prepared from choline chloride (ChCl) and oxalic acid (AT) in a molar ratio of 1:1. The preparation conditions of the acidic eutectic solvent and the preparation conditions of corn straw biochar were the same as in Example 1. The final biochar material was denoted as ChCl-AT-BC.

[0067] Comparative Example 4

[0068] Same as Example 1, except that the acidic eutectic solvent was prepared from choline chloride (ChCl) and citric acid (CA) in a molar ratio of 1:1. The preparation conditions of the acidic eutectic solvent and the preparation conditions of corn straw biochar were the same as in Example 1. The final biochar material was denoted as ChCl-CA-BC.

[0069] Comparative Example 5

[0070] Same as Example 1, except that the acidic eutectic solvent was prepared from choline chloride (ChCl) and malonic acid (MA) in a molar ratio of 1:1. The preparation conditions of the acidic eutectic solvent and the preparation conditions of corn straw biochar were the same as in Example 1. The final biochar material was denoted as ChCl-MA-BC.

[0071] Comparative Example 6

[0072] Same as Example 1, except that the acidic eutectic solvent was prepared by choline chloride (ChCl) and succinic acid (SuA) in a molar ratio of 1:1. The preparation conditions of the acidic eutectic solvent and the preparation conditions of corn straw biochar were the same as in Example 1. The final biochar material was denoted as ChCl-SuA-BC.

[0073] Test Example 1

[0074] Morphological, structural, and compositional characteristics

[0075] (1) Elemental content analysis

[0076] The contents of C, H, O, N, and S in the ChCl-MS-BC biochar and corn straw biomass powder prepared by carbonization at different temperatures in Examples 1-4 were determined by organic elemental analysis. The results are shown in Table 1.

[0077] Table 1

[0078]

[0079] Table 1 shows that the elemental contents of biochar materials prepared at different carbonization temperatures differed from those of raw corn stalk biomass. Specifically, the carbon content of the biochar increased with increasing carbonization temperature, indicating that higher temperatures are more conducive to the carbonization of biomass in the DES solvent system. Furthermore, during carbonization, while the carbon content increased with increasing carbonization temperature, the oxygen content of the biochar slightly decreased. The oxygen content of ChCl-MS-BC suggests that the biochar formed from acidic DES carbonization of corn stalks has a relatively rich number of oxygen-containing functional groups on its surface. In addition, the sulfur content of the biochar increased compared to uncarbonized biomass, indicating that the sulfur from methanesulfonic acid is retained on the biochar surface, providing additional active sites for the activation of persulfate.

[0080] (2) Scanning electron microscopy (SEM) detection

[0081] Figure 1 SEM images of ChCl-MS-BC biochar prepared by carbonization at different temperatures in Examples 1-4 are shown. a) and b) show the morphology of ChCl-MS-BC prepared by carbonization at 90 °C and 110 °C, respectively; c) and d) show the morphology of ChCl-MS-BC prepared by carbonization at 130 °C and 150 °C, respectively. Observation allows for analysis of the microstructure and pore structure of the biochar materials. Specifically, it can be seen that all four types of biochar are predominantly irregular granular structures with abundant wrinkles and pores on the surface. This may be attributed to the structural changes in biomass and the release of volatile substances during hydrothermal carbonization, providing the biochar with a considerable specific surface area. This surface morphology provides the biochar with numerous active sites for adsorption and catalysis.

[0082] (3) X-ray spectroscopy (EDS) detection

[0083] Figure 2 The EDS image of the ChCl-MS-BC biochar prepared in Example 1 shows the surface elemental distribution of the biochar material. It can be seen that the main elements present on the surface of ChCl-MS-BC are C, N, and O, with a small amount of Cl. The presence of chlorine (Cl) can be attributed to the ChCl content of the eutectic solvent used in the preparation. From the oxygen content of ChCl-MS-BC, it can be inferred that the biochar formed by carbonizing corn stalks with an acidic eutectic solvent has relatively abundant oxygen-containing functional groups on its surface.

[0084] (4) Infrared spectroscopy test

[0085] Figure 3 The images show the infrared spectra of ChCl-MS-BC biochar prepared by carbonization at different temperatures in Examples 1-4. It can be seen that the surface of ChCl-MS-BC contains a very rich number of oxygen-containing functional groups, including those at 3400 cm⁻¹. -1 The characteristic absorption peak of OH around 1750 cm⁻¹ -1 The characteristic absorption peaks of C=O around the left and right and at 1100 cm⁻¹ -1 The CO characteristic absorption peaks around the left and right, along with these abundant oxygen-containing functional groups, provide a large number of catalytic active sites for ChCl-MS-BC.

[0086] (5) Raman spectroscopy (XPS) test

[0087] Figure 4 XPS scans of ChCl-MS-BC biochar prepared by carbonization at different temperatures in Examples 1-4 are shown. In the image, a represents the fitting results for C1s, and b represents the fitting results for O1s. The C1s peak is mainly composed of CC / C=C, CO, and C=O, while the O1s fitting results are mainly composed of OH, CO, and C=O chemical bonds. The results indicate that the ChCl-MS-BC structure contains a large number of oxygen-containing functional groups, mainly OH, CO, C=O, and -COOH. These abundant oxygen-containing functional groups can provide a large number of active sites for BC-activated sodium persulfate (PDS). Furthermore, it was found that the percentage of CC / C=C bonds increases with increasing carbonization temperature, while the percentage of oxygen-containing functional groups decreases with increasing carbonization temperature.

[0088] Application Example 1

[0089] Performance testing of biochar prepared by carbonization with different acidic eutectic solvents (biochar prepared in Example 1 or Comparative Examples 1-6) on the degradation of flufenacet by activated sodium persulfate (PDS).

[0090] Degradation conditions: The study on the degradation of flumethrin by PDS activated by biochar in water was carried out in a 150 mL beaker at 25 °C using a magnetic stirrer. First, a flumethrin acetonitrile solution with a concentration of 2000 mg / L and a PDS solution with a concentration of 100 mmol / L were prepared as stock solutions. The degradation system was set as an aqueous solution with a total volume of 100 mL. A certain amount of PDS stock solution and flumethrin stock solution were added according to the predetermined concentration (the final concentration of flumethrin in the aqueous solution was 40 mg / L and the concentration of PDS was 5 mmol / L), and water was added to bring the volume to 100 mL. Finally, 30 mg of biochar (the biochar prepared in Example 1 or Comparative Examples 1-6) was added to start the degradation reaction (at 25 °C), and the timer was started at the same time. Samples were taken at time points of 0 min, 5 min, 10 min, 20 min, 30 min, 40 min, 60 min, 80 min, and 100 min. 0.8 mL of the mixed solution was extracted and filtered through a 0.22 µm aqueous filter membrane. 0.5 mL of the filtrate was then mixed with 0.5 mL of methanol to quench free radical reactions. Finally, the concentration of flufenoxuron in the sample was analyzed by liquid chromatography (C0.05). e The test results are as follows: Figure 5 As shown.

[0091] Figure 5 The degradation experiments showed that ChCl-MS-BC achieved the highest catalytic degradation efficiency for flumetsulam within 100 min, reaching a removal rate of 94.13% for the target compound with an initial concentration (CO) of 40 mg / L. ChCl-AT-BC was the second highest, but its degradation efficiency for flumetsulam decreased after 20 min, with a removal rate of only 17.67% at 100 min. The other five BCs exhibited poor catalytic degradation performance for flumetsulam, with removal rates all less than 10% at 100 min. This indicates that biochar prepared using a strongly acidic eutectic solvent (ChCl-MS; the smaller the pKa of the hydrogen bond donor organic acid in the eutectic solvent, the stronger the acidity of the eutectic solvent; among MS, FA, AcA, AT, CA, MA, and SuA, MS has the smallest pKa) has better catalytic performance. The stronger the acidity of the eutectic solvent, the better the carbonization effect on corn straw biomass. On the other hand, the doping of sulfur also provides more active sites for biochar, and correspondingly, the ability to activate PDS to degrade flumethrin is also stronger.

[0092] Application Example 2

[0093] Effect of different pH values ​​on the degradation performance of flusulfanilamide by ChCl-MS-BC activated sodium persulfate (PDS)

[0094] Flumetsulam, a high-dose, widely applicable, and long-residual herbicide, can easily cause long-term environmental impacts after application. The ether bonds, aromatic rings, amino groups, and halogenated groups in flumetsulam's structure are highly susceptible to reactive free radicals generated by advanced oxidation techniques (such as hydroxyl radicals (·OH) and sulfate radicals (SO4·)). - This process leads to the breaking of ether bonds, free radical addition to aromatic rings to form hydroxylated products, conversion of amino groups to nitrated products, and halogen bond cleavage, resulting in defluorination and dechlorination. Therefore, advanced oxidation technology using biochar-activated persulfate has great potential for degrading and removing flumethrin pesticide residues. Considering the complexity of actual aquatic environments, this invention investigates the effect of solution pH on the degradation performance of flumethrin by biochar-activated PDS.

[0095] The degradation conditions for the effect of solution pH on the degradation performance of flufenoxuron by ChCl-MS-BC activated sodium persulfate (PDS) were as follows: First, a flufenoxuron acetonitrile solution with a concentration of 2000 mg / L and a PDS solution with a concentration of 100 mmol / L were prepared as additive stock solutions. The degradation system was set as an aqueous solution with a total volume of 100 mL. A certain amount of PDS stock solution and flufenoxuron stock solution were added according to the predetermined concentration (the final concentration of flufenoxuron in the aqueous solution was 40 mg / L and the concentration of PDS was 5 mmol / L), and water was added to bring the volume to 100 mL (the solution temperature was 25 ℃). Then, the pH of the solution was adjusted to 7, 8, 9, 10, and 11, and 30 mg of biochar material (ChCl-MS-BC prepared in Example 1) was added. The solution was stirred in a magnetic stirrer and the pH was adjusted at 0 min, 5 min, 10 min, 20 min, 30 min, 40 min, 60 min, 80 min, and 100 min, respectively. Sampling was performed at the min time point, and 0.8 mL of the mixed solution was extracted and filtered through a 0.22 µm aqueous filter membrane. Then, 0.5 mL of the filtrate was mixed with 0.5 mL of methanol to quench the free radical reaction. Finally, the concentration of flusulfanilamide in the sample was analyzed by liquid chromatography.

[0096] Flumetsulam, a weakly acidic pesticide, is mainly found in water with a pH ≥ 7; therefore, this invention investigated the degradation performance of flumetsulam in water using a ChCl-MS-BC / PDS system within a pH range of 7-11. The results are as follows... Figure 6The figure shows the trend of ChCl-MS-BC / PDS degradation performance for flusulfanilamide in the pH range of 7-11. It can be seen that the results indicate that ChCl-MS-BC / PDS maintains good degradation performance for flusulfanilamide in water between pH 7 and 9, but the degradation rate begins to slow down with continuous increase in pH, and the degradation performance gradually decreases after pH ≥ 10. The reason for the decrease in degradation performance due to increased pH may be due to the reduced degradation performance of hydroxide ions against SO4· ... - The reaction consumption leads to a decrease in degradation efficiency. The adsorption capacity gradually increases from acidic to neutral, reaching its maximum at pH≈7, and then decreases significantly under alkaline conditions. Therefore, the optimal effect of biochar-activated PDS in degrading flufenoxuron occurs in neutral to slightly alkaline conditions, which is of great significance for practical applications because environmental water bodies are often neutral to slightly alkaline.

[0097] Application Example 3

[0098] Identification of active species in the ChCl-MS-BC activated sodium persulfate (PDS) degradation system for flumethrin

[0099] This invention incorporates free radical quenching experiments and electron paramagnetic resonance (EPR) detection. Specifically, a 2000 mg / L flumetsulam acetonitrile solution and a 100 mmol / L PDS solution were first prepared as additive stock solutions. The degradation system was set as a 100 mL aqueous solution. A certain amount of PDS stock solution and flumetsulam stock solution were added according to predetermined concentrations (40 mg / L flumetsulam and 5 mmol / L PDS in the final aqueous solution), and water was added to bring the volume to 100 mL (solution temperature: 25 ℃, pH=7). Then, 30 mg of biochar material was added, and different quenchers (5 mmol / L each) were added to the reaction system for quenching (the experimental group without any quenchers served as the blank control group). The mixture was stirred in a magnetic stirrer at 0 min, 5 min, 10 min, 20 min, 30 min, 40 min, 60 min, and 80 min. Samples were taken at 100 min and 100 min time points. 0.8 mL of the mixed solution was extracted and filtered through a 0.22 µm aqueous filter membrane. 0.5 mL of the filtrate was then mixed with 0.5 mL of methanol to quench the free radical reaction. Finally, the concentration of flufenoxuron in the sample was analyzed by liquid chromatography. The type of active substance was inferred by the effect of the quencher on the degradation efficiency. The test results are as follows: Figure 7 As shown in a, the results indicate that ·OH and SO4· -It is the main ROS leading to the degradation of the ChCl-MS-BC / PDS system. The most significant inhibitory effect was observed due to the scavenging of hydroxyl radicals by TBA. Furthermore, the addition of 5 mmol / L p-BQ resulted in a decrease in degradation rate from 88.92% to 61.69%. This implies that O2· - It also participated in the degradation process.

[0100] To further directly observe the generation of reactive free radicals, this invention utilizes spin trapping technology combined with EPR to test the reaction solution. Specifically, DMPO is used as the trapping agent, and EPR spectroscopy is used to further identify the active ROS during the degradation process. The results are as follows: Figure 7 Figures b, c, and d show the EPR spectra of the reaction solution after the addition of PDS in the presence of ChCl-MS-BC. Figure b shows two characteristic signal peaks with intensity ratios of 1:2:2:1 and 1:1:1:1:1, corresponding to ·OH and SO4·, respectively. - The characteristic peaks shown by c and d correspond to O2· - and 1 O2 active groups. At mins 2, 5, and 10, the signal values ​​gradually increased with the progress of the catalytic reaction. These results confirm that ·OH and SO4· - O2· - as well as 1 O2 is the main active free radical in the ChCl-MS-BC / PDS (i.e., BC / PDS) degradation system.

[0101] In summary, this invention uses corn stalks as raw material and optimizes the preparation method of biochar using an acidic eutectic solvent. It adopts a greener and more efficient method to prepare biochar for the degradation of the long-residual herbicide flusulfanilamide in the environment. The structural characteristics, catalytic performance and degradation mechanism of the material were systematically investigated, providing a new approach for the management of long-residual herbicides in the environment and the resource utilization of straw.

[0102] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing biochar using an acidic eutectic solvent, characterized in that, Includes the following steps: Biomass powder and an acidic eutectic solvent are mixed and heated under reflux to produce biochar. The acidic eutectic solvent uses choline chloride as a hydrogen bond acceptor and methanesulfonic acid as a hydrogen bond donor.

2. The method for preparing biochar using an acidic eutectic solvent as described in claim 1, characterized in that, The preparation steps of the acidic eutectic solvent include: mixing choline chloride and methanesulfonic acid, heating and stirring to obtain the eutectic solvent.

3. The method for preparing biochar using an acidic eutectic solvent as described in claim 2, characterized in that, The molar ratio of choline chloride to methanesulfonic acid is 1:1-1.

5.

4. The method for preparing biochar using an acidic eutectic solvent as described in claim 2, characterized in that, The heating and stirring temperature is 80-100 ℃, and the time is 1-3 h.

5. The method for preparing biochar using an acidic eutectic solvent as described in claim 1, characterized in that, The mass ratio of the biomass powder to the acidic eutectic solvent is 1.5:20-30.

6. The method for preparing biochar using an acidic eutectic solvent as described in claim 1, characterized in that, The heating reflux reaction is carried out at a temperature of 90-150 °C for 2-5 h.

7. The method for preparing biochar using an acidic eutectic solvent as described in claim 1, characterized in that, The biomass powder is obtained by drying and pulverizing corn stalks.

8. Biochar prepared by a method for preparing biochar using an acidic eutectic solvent according to any one of claims 1-7.

9. The application of the biochar as described in claim 8 in the activation of persulfate degradation of flumethrin in water.

10. The application as described in claim 9, characterized in that, The application steps include: adding persulfate and the biochar of claim 8 to a water body containing flusulfanilamide to carry out a degradation reaction.

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